Re-Excision After Positive Margins in Breast-Conserving Surgery: Can a Risk-Based Strategy Avoid Unnecessary Surgery?

<b>Background:</b> Re-excision after breast-conserving surgery (BCS) is routinely recommended when positive margins are found. However, secondary surgery often reveals no residual disease, exposing patients to unnecessary interventions that compromise cosmetic outcomes, increase costs, and reduce quality of life. This study investigates clinicopathological predictors of a residual tumour to identify low-risk patients who may safely avoid re-excision. <b>Methods:</b> We conducted a retrospective cohort study of 135 patients who underwent reoperation for positive margins following BCS at the Breast Unit of Fondazione Policlinico Universitario A. Gemelli IRCCS in Rome, between 2019 and 2024. Data on patient demographics, tumour characteristics, and histopathological findings were analyzed using univariate and multivariate models to identify predictors of residual disease. <b>Results:</b> A residual tumour was detected in 66 of 135 patients (48.9%). In the remaining 69 cases (51.1%), no residual disease was found, indicating that re-excision may have been unnecessary. Multifocality (<i>p</i> < 0.01), lymphovascular invasion (LVI) (<i>p</i> < 0.05), and involvement of ≥2 margins (<i>p</i> < 0.05) were independently associated with the residual tumour. Patients with unifocal disease, absence of LVI, and a single positive margin had a significantly lower risk of residual disease. <b>Conclusions:</b> Over half of re-excisions performed for positive margins may be avoidable. A risk-adapted approach incorporating tumour focality, LVI status, and margin involvement can help identify patients for whom secondary surgery may offer limited benefits. These findings support a more individualized strategy to margin management in BCS aimed at reducing overtreatment without compromising oncologic safety.